1. Field of the Invention
The present invention relates to cochlear implant prostheses and in particular to a method and apparatus for adjusting the operation of such a prosthesis in order to optimize the benefit of the therapy provided by the prosthesis to a user.
2. Related Art
It is known that individual patients using a cochlear implant system differ in their ability to benefit from different speech coding strategies. These coding strategies may differ in the number of channels activated, the dynamic or fixed allocation of channels to electrodes and the rate of stimulation for each channel. For example, some patients show significant improvements in open-set speech understanding when converting from a relatively low rate of stimulation of 250 Hz per channel (for example as provided by the SPEAK stimulation strategy used in some of the products manufactured by the Cochlear Limited, NSW, AU) to rates of 1200 Hz per channel or more (for example as provided by the ACE stimulation strategy also used in some of the products manufactured by the Cochlear Limited, NSW, AU) while other stimulation parameters, such as the number of channels and their allocation to electrodes remain unchanged. Other patients show no improvement, or even a reduction in benefit, when the stimulation rate is increased from low rates to high rates.
Consequently at present the adjustment of operation of the implant in order to optimize the benefit of the therapy provided to a patient by a cochlear implant prosthesis is to some extent a hit-or-miss affair. In particular comments must be sought from the patient as to whether or not the benefit of the prosthesis is improved or decreased upon making an adjustment in operation. There are a number of problems associated with this prior art approach. For example the adjustment is not made according to any quantitative parameter but rather is based on the somewhat subjective judgments of the patient.
Furthermore some patients, for example young children, may not be able to readily indicate an improvement or decrease in the quality of their hearing perception during the adjustment process. Yet a further problem is that the present approach does not readily lend itself to automation, relying as it does on the conscious feedback of the patient. It is an object of the present invention to provide a method for setting a cochlear implant prosthesis to an appropriate operation mode which overcomes the previously described problems.